1/* 2 * Copyright (C) 2008 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17package com.google.common.io; 18 19import com.google.common.base.Preconditions; 20 21import java.io.IOException; 22import java.io.Reader; 23import java.util.Iterator; 24 25import javax.annotation.Nullable; 26 27/** 28 * A {@link Reader} that concatenates multiple readers. 29 * 30 * @author Bin Zhu 31 * @since 1.0 32 */ 33class MultiReader extends Reader { 34 private final Iterator<? extends CharSource> it; 35 private Reader current; 36 37 MultiReader(Iterator<? extends CharSource> readers) throws IOException { 38 this.it = readers; 39 advance(); 40 } 41 42 /** 43 * Closes the current reader and opens the next one, if any. 44 */ 45 private void advance() throws IOException { 46 close(); 47 if (it.hasNext()) { 48 current = it.next().openStream(); 49 } 50 } 51 52 @Override public int read(@Nullable char cbuf[], int off, int len) throws IOException { 53 if (current == null) { 54 return -1; 55 } 56 int result = current.read(cbuf, off, len); 57 if (result == -1) { 58 advance(); 59 return read(cbuf, off, len); 60 } 61 return result; 62 } 63 64 @Override public long skip(long n) throws IOException { 65 Preconditions.checkArgument(n >= 0, "n is negative"); 66 if (n > 0) { 67 while (current != null) { 68 long result = current.skip(n); 69 if (result > 0) { 70 return result; 71 } 72 advance(); 73 } 74 } 75 return 0; 76 } 77 78 @Override public boolean ready() throws IOException { 79 return (current != null) && current.ready(); 80 } 81 82 @Override public void close() throws IOException { 83 if (current != null) { 84 try { 85 current.close(); 86 } finally { 87 current = null; 88 } 89 } 90 } 91} 92